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https://github.com/revng/revng
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Alvise de Faveri
43ae7a91cb
Add a step that recognizes if two subtrees of a union node are topologically equivalent and merges them. This corresponds to removing duplicate fields in unions. This deduplication was prevously done while emitting layouts. A check is inserted into DLAMakeLayouts to assert that, after constructing unions, no union has only one child, which could be the case if we didn't deduplicate union fields in the graph.
99 lines
2.7 KiB
C++
99 lines
2.7 KiB
C++
//
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// Copyright (c) rev.ng Srls. See LICENSE.md for details.
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//
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#include "llvm/ADT/PostOrderIterator.h"
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#include "llvm/ADT/STLExtras.h"
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#include "revng/Support/Assert.h"
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#include "revng/Support/Debug.h"
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#include "revng-c/DataLayoutAnalysis/DLATypeSystem.h"
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#include "../DLAHelpers.h"
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#include "DLAStep.h"
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using LTSN = dla::LayoutTypeSystemNode;
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using VecToCollapseT = std::vector<LTSN *>;
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using namespace llvm;
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static Logger<> Log("dla-collapse-single-child");
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namespace dla {
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bool CollapseSingleChild::collapseSingle(LayoutTypeSystem &TS,
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LayoutTypeSystemNode *Node) {
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bool Changed = false;
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auto HasSingleChild = [](const LTSN *Node) {
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return (Node->Successors.size() == 1);
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};
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auto ChildIsInstanceOrInheritance = [](const LTSN *Node) {
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auto &Child = *Node->Successors.begin();
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return (isInstanceEdge(Child) or isInheritanceEdge(Child));
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};
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auto HasAtMostOneParent = [](const LTSN *Node) {
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return (Node->Predecessors.size() <= 1);
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};
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// Get nodes that have a single instance or inheritance child
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if (HasSingleChild(Node) and ChildIsInstanceOrInheritance(Node)) {
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auto &ChildEdge = *(Node->Successors.begin());
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const unsigned ChildOffset = isInheritanceEdge(ChildEdge) ?
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0U :
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ChildEdge.second->getOffsetExpr().Offset;
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auto &ToMerge = ChildEdge.first;
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// Don't collapse if the child has more than one parent
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if (not HasAtMostOneParent(ToMerge))
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return false;
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// Collapse only if the child is at offset 0
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if (ChildOffset == 0) {
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revng_log(Log, "Collapsing " << ToMerge->ID << " into " << Node->ID);
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const unsigned ChildSize = ToMerge->Size;
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revng_assert(Node->Size == 0 or Node->Size == ChildSize);
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// Merge single child into parent
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TS.mergeNodes({ /*Into=*/Node, /*From=*/ToMerge });
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Node->Size = ChildSize;
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Changed = true;
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}
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}
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return Changed;
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}
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bool CollapseSingleChild::runOnTypeSystem(LayoutTypeSystem &TS) {
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bool Changed = false;
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if (VerifyLog.isEnabled())
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revng_assert(TS.verifyDAG() and TS.verifyInheritanceTree());
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if (Log.isEnabled())
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TS.dumpDotOnFile("before-collapse-single-child.dot");
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for (LTSN *Root : llvm::nodes(&TS)) {
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revng_assert(Root != nullptr);
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if (not isRoot(Root))
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continue;
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for (LTSN *Node : post_order(Root))
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Changed |= collapseSingle(TS, Node);
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}
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if (Log.isEnabled())
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TS.dumpDotOnFile("after-collapse-single-child.dot");
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if (VerifyLog.isEnabled()) {
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revng_assert(TS.verifyInheritanceDAG());
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revng_assert(TS.verifyInheritanceTree());
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}
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return Changed;
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}
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} // end namespace dla
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